In the manufacture of molded records, a thermoplastic material is molded between a pair of flat disc shaped members referred to as stampers. The stampers used in the molding process are metal parts which have defined in their molding surface a mirror image of the surface relief pattern desired to be molded into the surface of the record. It is important that the molding surface of the stamper used to press the record be free of scratches or other surface imperfections, since these will be reproduced in the molded record and will cause defects on playback.
The stampers themselves are the end product of a multistep manufacturing process. The initial step in the process is to record the desired program information on a recording tape such as a magnetic tape. The tape is then used to drive a cutter head which cuts a surface relief pattern corresponding to the information recorded on the tape into a recording substrate.
The patterned surface of the recording substrate is then replicated by electroforming a metal, such as bright nickel, on the surface of the recording substrate. The part which is electroformed on the surface of the substrate is referred to as a master. The resulting master must be very carefully separated from the recording substrate to prevent damage to the master.
The above steps are repeated, using the master to electroform a series of parts resulting in a plurality of stampers being generated from a single master.
One area which has been found to be extremely troublesome with regard to the introduction of surface defects is the separation of the replicas from the matrixes on which the replicas are formed. One conventional method used for the separation is to manually split the replica from the matrix with a hand held knife and then physically strip the replica from the surface of the matrix. This method has many inherent disadvantages. It is not uncommon for the operators to plunge the knives used for the separation too far into the seam between the matrix and replica and scratch or otherwise damage the recorded surface of the replica, the matrix, or both parts. Even if a correct cut is made at the outer edge, the force required to separate the replica from the matrix often causes one of the parts to be bent or otherwise damaged beyond repair. A still further problem of the manual method of separation is that the parts often separate prematurely and tend to slide over the surface of each other and cause surface damage to either one or both of the parts. The manual method of separation also requires the excessive manual handling of the replicas and the matrixes during separation which inevitably results in the operator contacting the surface of the parts leaving oily deposits or the like on the surface which interfere with further matrixing processes.
Various suggestions have been made in the art to improve the separation of the replicas from matrixes. One such suggestion was made by Lock in U.S. Pat. No. 4,381,964 entitled, "Method and Apparatus for Separating a Stamper and a Mold" where it was suggested to inject a gas under pressure at the center hole between the stamper and the mold so as to force the stamper from the surface of the mold. The apparatus of the Lock invention works with reasonable success under strictly controlled laboratory conditions, but was found under production conditions to be at best marginal due to the normal production variations in the electroformed parts. In addition, the apparatus of Lock is expensive to build, operate and maintain.
Other methods and apparatus have been suggested but again with at best erratic or poor results being obtained in the separation of replicas from matrixes.
It would be desirable thus to have an apparatus for separating replicas from the matrixes on which they are formed which would be inexpensive to construct, relatively simple to operate and which would provide reliable results in separating the replicas from matrixes without causing damage to either the matrixes or the replicas.